Three gardaí were injured and 23 people were arrested after anti-lockdown protesters clashed with gardaí in Dublin on Saturday.
A Garda statement said one of the gardaí required treatment in hospital.
Garda Commissioner Drew Harris accused protesters of being intent on assaulting and injuring members of the force during a demonstration which begun outside St Stephen’s Green.
Mr Harris said only by “good grace and quick thinking” did gardaí escape serious injury when a firework was fired at them from point-blank rage.
Gardaí said the arrested were made under public order legislation and those arrested would appear at the Courts of Criminal Justice on Saturday night.
Taoiseach Micheál Martin condemned the demonstration “which posed an unacceptable risk to both the public and gardaí”.
Antoinette Cunningham, the general secretary of the Association of Garda Sergeants and Inspectors said: “It is utterly horrifying to see our members being placed under incredible stress, pressure and danger.
"These types of protests are completely unacceptable and show a wilful and blatant disregard for all members of An Garda Síochána on duty today.
“To see missiles being deliberately fired and directed into our unarmed members is truly shocking and highlights the dangerous and intensive element of policing this part of Covid-19.”
Hundreds of people gathered in the early afternoon outside St Stephen’s Green, which the Office of Public Works were instructed to close by gardaí. The protests against Covid-19 restrictions had been scheduled to start at 2pm but there was a large crowd gathered long before that.
Gardaí had clearly planned for keeping the crowd contained. Barriers kept the crowd of about 300 corralled into the Grafton Street area. After a short time the crowd started to push against the barriers and the phalanx of gardaí keeping them back started to thicken.
There were plenty of Irish Republic and Tricolour flags on display. National Party volunteers handed out fliers.
Most of the protesters were not wearing masks. One protester shouted at gardaí: “You’re a f**king scumbag. This is our country not yours.”
After a stand-off lasting about 20 minutes the crowds made their way to the GPO in O’Connell Street where traffic was stopped for much of the afternoon.
The Luas green line was stopped completely for a time before services resumed. Services between St Stephen’s Green and O’Connell Street remain unavailable.
A woman stood outside the portico of the GPO and played a recording of the Proclamation to the crowd.
Mr Harris said the protests were planned as a test case to see what they could get away with and how many people would turn up.
“We are very much on our guard now about what happens next,” he said. “We are going to follow through with a major investigation. There are plenty of individuals who have committed offences today and which we will see them being brought to justice.”
Mr Harris said gardaí had been monitoring social media and expected hundreds to turn up to the anti-lockdown protests on Saturday.
He questioned why anybody would bring a firework to a protest if their intention was to peacefully protest.
He said the individual who let off the firework would now be the subject of a criminal investigation and an investigating officer would be appointed. The video footage of the firework being let off may be used in evidence.
“We will very likely identify that individual and bring him to justice,” he said.
“This was a protest which sits outside the normal behaviour of our society and has to be seen as such.
“These are not mainstream groups. The vast majority of our society is complying with regulations and they are living within the regulations as best they can in order to suppress Covid-19.
“We will follow through with an investigation. The operation is ongoing and we will ensure that the city centre is safe and secure for the rest of the night.”
On Sunday, the commissioner said the vast majority of those who took part in the protest “belong to a number of factions including anti-vaccine, anti-mask and anti-lockdown protestors, far right groups, and those intent on trouble and disorder”.
The commissioner was clarifying statements he made on Saturday, in which he said the groups involved were a mix that included the far-left. “Despite initial indications, following further investigation, there is no corroborated evidence of extreme left factions being involved,” he said on Sunday. He also thanked the public for their messages of goodwill for the gardaí who policed the protest.
In a statement on Saturday evening, the Taoiseach said: “The large gathering, in the face of ongoing Covid-19 restrictions, showed a complete lack of respect to the people who have made huge sacrifices during this pandemic.
“Nor can we tolerate the thuggish behaviour or attacks on gardaí, who have the public’s utmost respect as they continue to protect and serve our society in difficult circumstances.
“There can be no justification for the march or the violence that unfolded, and I pay tribute to members of An Garda Síochána who moved quickly to make arrests and restore order.”
Minister for Higher Education Simon Harris criticised the actions of the protesters describing it as “pure thuggery”. It’s not a “protest”. “It’s an attack on our national effort. The abuse directed at the gardaí is sickening & shameful,” he tweeted.